Effects of crystalloid on lung fluid balance after smoke inhalation

Inhalation Injury, Respiratory Failure, and Ventilator Support in Acute Burn Care

Sustaining an inhalation injury increases the risk of severe complications and mortality. Current evidential support to guide treatment of the injury or subsequent complications is lacking, as studies either exclude inhalation injury or design limit inferences that can be made. Conventional ventilator modes are most commonly used, but there is no consensus on optimal strategies. Settings should be customized to patient tolerance and response. Data for pharmacotherapy adjunctive treatments are limited.

Surviving Sepsis After Burn Campaign

INTRODUCTION

The Surviving Sepsis Campaign was developed to improve outcomes for all patients with sepsis. Despite sepsis being the primary cause of death after thermal injury, burns have always been excluded from the Surviving Sepsis efforts. To improve sepsis outcomes in burn patients, an international group of burn experts developed the Surviving Sepsis After Burn Campaign (SSABC) as a testable guideline to improve burn sepsis outcomes.

METHODS

The International Society for Burn Injuries (ISBI) reached out to regional or national burn organizations to recommend members to participate in the program. Two members of the ISBI developed specific "patient/population, intervention, comparison and outcome" (PICO) questions that paralleled the 2021 Surviving Sepsis Campaign [1]. SSABC participants were asked to search the current literature and rate its quality for each topic. At the Congress of the ISBI, in Guadalajara, Mexico, August 28, 2022, a majority of the participants met to create "statements" based on the literature. The "summary statements" were then sent to all members for comment with the hope of developing an 80% consensus. After four reviews, a consensus statement for each topic was created or "no consensus" was reported.

RESULTS

The committee developed sixty statements within fourteen topics that provide guidance for the early treatment of sepsis in burn patients. These statements should be used to improve the care of sepsis in burn patients. The statements should not be considered as "static" comments but should rather be used as guidelines for future testing of the best treatments for sepsis in burn patients. They should be updated on a regular basis.

CONCLUSION

Members of the burn community from the around the world have developed the Surviving Sepsis After Burn Campaign guidelines with the goal of improving the outcome of sepsis in burn patients.

Tidal volume challenge to predict preload responsiveness in patients with acute respiratory distress syndrome under prone position

Background

Prone position is frequently used in patients with acute respiratory distress syndrome (ARDS), especially during the Coronavirus disease 2019 pandemic. Our study investigated the ability of pulse pressure variation (PPV) and its changes during a tidal volume challenge (TVC) to assess preload responsiveness in ARDS patients under prone position.

Methods

This was a prospective study conducted in a 25-bed intensive care unit at a university hospital. We included patients with ARDS under prone position, ventilated with 6 mL/kg tidal volume and monitored by a transpulmonary thermodilution device. We measured PPV and its changes during a TVC (ΔPPV TVC6–8) after increasing the tidal volume from 6 to 8 mL/kg for one minute. Changes in cardiac index (CI) during a Trendelenburg maneuver (ΔCITREND) and during end-expiratory occlusion (EEO) at 8 mL/kg tidal volume (ΔCI EEO8) were recorded. Preload responsiveness was defined by both ΔCITREND ≥ 8% and ΔCI EEO8 ≥ 5%. Preload unresponsiveness was defined by both ΔCITREND < 8% and ΔCI EEO8 < 5%.

Results

Eighty-four sets of measurements were analyzed in 58 patients. Before prone positioning, the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen was 104 ± 27 mmHg. At the inclusion time, patients were under prone position for 11 (2–14) hours. Norepinephrine was administered in 83% of cases with a dose of 0.25 (0.15–0.42) µg/kg/min. The positive end-expiratory pressure was 14 (11–16) cmH2O. The driving pressure was 12 (10–17) cmH2O, and the respiratory system compliance was 32 (22–40) mL/cmH2O. Preload responsiveness was detected in 42 cases. An absolute change in PPV ≥ 3.5% during a TVC assessed preload responsiveness with an area under the receiver operating characteristics (AUROC) curve of 0.94 ± 0.03 (sensitivity: 98%, specificity: 86%) better than that of baseline PPV (0.85 ± 0.05; p = 0.047). In the 56 cases where baseline PPV was inconclusive (≥ 4% and < 11%), ΔPPV TVC6–8 ≥ 3.5% still enabled to reliably assess preload responsiveness (AUROC: 0.91 ± 0.05, sensitivity: 97%, specificity: 81%; p < 0.01 vs. baseline PPV).

Conclusion

In patients with ARDS under low tidal volume ventilation during prone position, the changes in PPV during a TVC can reliably assess preload responsiveness without the need for cardiac output measurements.

Trial registration: ClinicalTrials.gov (NCT04457739). Registered 30 June 2020 —Retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT04457739

Current consensus and controversies in major burns management

Most doctors in Britain receive some training in the care of the burned patient, if not as an undergraduate then as part of training in accident and emergency medicine or in the Advanced Trauma Life Support (ATLS®) course. Because major burn injury presents infrequently to the average district hospital, most of this training is rusty by the time it is needed. Further, most have little opportunity to catch up with developments in this very specialized area of trauma medicine.

This paper aims to address some of these shortcomings by describing recent advances in burn care and highlighting areas of current debate. The fluids used for resuscitation, improved options for treatment, the status of ongoing discussions about treatment facilities and the state of the art in managing smoke inhalation are reviewed. Some pointers to the future and to avenues for research are suggested.

Meta-analysis of thyroidectomy with ultrasonic dissector versus conventional clamp and tie

Background

We conducted a systematic review to evaluate the role of Ultrasonic dissector (UAS) versus conventional clamp and tie in thyroidectomy.

Materials and methods

We searched for all published RCT in into electronic databases. To be included in the analysis, the studies had to compare thyroidectomy with UAS versus conventional vessel ligation and tight (conventional technique = CT). The following outcomes were used to compare the total thyroidectomy group with UAS versus CT group: operative duration, operative blood loss, overall drainage volume during the first 24 hours, transiet laryngeal nerve palsy, permanent laryngeal nerve palsy, transiet hypocalcaemia and permanent hypocalcaemia.

Results

There are currently 7 RCT on this issue to compare thyroidectomy with UAS versus CT. From the analysis of these studies it was possible to confront 608 cases: 303 undergoing to thyroidectomy with UAS versus 305 that were treated with CT. Actually, it was shown a relevant advantage of cost-effectiveness in patients treated with UAS; there is a statistically significant reduction of the operative duration (weighted mean difference [WMD], -18.74 minutes; 95% confidence interval [CI], (-26.97 to -10.52 minutes) (P = 0.00001), intraoperative blood loss (WMD, -60.10 mL; 95% CI, -117.04 to 3.16 mL) (P = 0.04) and overall drainage volume (WMD, -35.30 mL; 95% CI, -49.24 to 21.36 mL) (P = 0.00001) in the patients underwent thyroidectomy with UAS. Although the analysis showed that the patients who were treated with USA presented more favourable results in incidence of post-operative complications (transient laryngeal nerve palsy: P = 0.11; permanent laryngeal nerve palsy: not estimable; transient hypocalcaemia: P = 0.24; permanent hypocalcaemia: P = 0.45), these data didn't present statistical relevance.

Conclusion

This meta-analysis shown a relevant advantage only in terms of cost-effectiveness in patients treated with UAS; it is subsequent to statistically significant reduction of operation duration, intraoperative blood loss and of overall drainage volume during the first 24 hours. Although the analysis showed that the patients who were treated with UAS presented more favourable results in incidence of post-operative complications (transiet laryngeal nerve palsy; transiet hypocalcaemia and permanent hypocalcaemia), these data didn't present statistical relevance.

New method for evaluation of lung lymph flow rate with intact lymphatics in anaesthetized sheep

AIM

Lung lymph has commonly been studied using a lymph fistula created by tube cannulation into the efferent duct of the caudal mediastinal node in sheep. In this method, the tail region of the caudal mediastinal node is resected and the diaphragm is cauterized to exclude systemic lymph contamination, and cannulation is performed into one of the multiple efferent ducts originating from the caudal mediastinal node. Moreover, the pumping activity of lymphatics might be diminished by cannulation. Therefore, the purpose of the study was to evaluate the flow rate of lung lymph with maintenance of intact lymphatic networks around the caudal mediastinal node to the thoracic duct in sheep.

METHODS

An ultrasound transit-time flow meter was used to measure lung lymph flow. The thoracic duct was clamped just above the diaphragm and the flow probe was attached to the thoracic duct just after the last junction with an efferent duct from the caudal mediastinal node. The lung lymph flow rate was measured at baseline and under conditions of lung-oedema formation.

RESULTS

The baseline lung lymph flow rate in our model was three- to sixfold greater than values obtained with the cannulation method. With oedema-formation, the lung lymph flow rate was the same as that measured using cannulation.

CONCLUSION

The lung lymph flow was unexpectedly large under the conditions of the study, and our data suggest that the drainage effect of lymphatics is significant as a safety factor against pulmonary oedema formation.

Is high PEEP low volume ventilation in burn patients beneficial? A retrospective study of 61 patients

In burn care lung damage by inhalation injury is a major cause of mortality in burn patients. In the field of intensive care medicine ventilation strategies to reduce lung injury caused by ventilation are under investigation. The promising results of the application of pressure controlled high PEEP low volume (HPLV) ventilation prompted us to use this ventilation strategy in our burn ICU. To establish whether this ventilation regime is beneficial the charts of 61 consecutive patients needing artificial respiration were reviewed. A scoring system for PEEP level and tidal volume was developed and treatment groups with high PEEP and low volume and low PEEP high volume regimes were compared. No statistically significant differences could be found when comparing treatment versus mortality, the number of pulmonary complications or incidence of pneumothoraces. However, the trend showed a benefit in mortality for patients with an ABSI scoring up to 9, but at the same time pulmonary complications increase. The Horovitz oxygenation index showed no advantage for the HPLV Group. In a separate analysis we found a significant correlation between absolute PEEP and mortality. The correlation between PEEP level and mortality is a dynamic factor predicting outcome, This not been described yet and can be an addition to the static ABSI score. Differences between ventilation strategies were not as evident as expected in this retrospective study, so prospective randomized studies are needed.

Burns resuscitation: what place albumin?

The Cochrane analysis of the use of albumin in critical illness has highlighted the need for more well-conducted studies on colloid use in burns. The lack of objectivity in the press regarding this material has compromised our ability to deliver those studies. The analysis provides no evidence that albumin is unsafe for the initial resuscitation of uncomplicated burns, and the fall in its use is more likely to be cost-related.

Segmental pulmonary vascular resistance following wood smoke inhalation

OBJECTIVES

To locate the specific site (i.e., pulmonary arteries, veins, or capillaries) of increased pulmonary vascular resistance after wood smoke inhalation and to demonstrate whether the prostanoids, thromboxane B2 or 6-keto-prostaglandin F1 alpha, play a role in these vascular resistance changes.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Laboratory at a university medical center.

SUBJECTS

Five mongrel dogs.

INTERVENTIONS

The isolated canine left lower lobe preparation was used to measure changes in the pressure drop across the pulmonary arteries, veins, and capillaries. The left lower lobe was surgically isolated and perfused by a pump primed with autologous blood. The arterial and venous occlusion technique and the vascular pressure-flow relationship were used to assess changes in pulmonary vascular resistance. After baseline measurements, the left lower lobe was exposed to wood smoke for 2.5 mins and measurements were repeated.

MEASUREMENTS AND MAIN RESULTS

Smoke exposure caused an immediate (5 mins post-inhalation) increase in the total pressure gradient across the lobe (baseline = 9.8 +/- 0.5 torr [1.3 +/- 0.06 kPa]); smoke inhalation = 24.3 +/- 3.9 torr [3.24 +/- 0.5 kPa]; p < .05). Total pressure drop was partitioned longitudinally into pressure drops across arteries, veins, and the middle vessels. The increase in total pressure drop was associated with a moderate increase in the pressure drop across the middle vessels (baseline = 1.1 +/- 0.2 torr [0.14 +/- 0.02 kPa]; smoke inhalation = 5.2 +/- 1.1 torr [0.69 +/- 0.14 kPa]; p < .05); a large increase in the pressure drop across the veins (baseline = 4.8 +/- 1.3 torr [0.64 +/- 0.17 kPa]; smoke inhalation = 20.7 +/- 3.4 torr [2.7 +/- 0.45 kPa]; p < .05), and no significant change in the pressure drop across the arteries (baseline = 3.7 +/- 0.4 torr [0.49 +/- 0.05 kPa]; smoke inhalation = 4.8 +/- 0.5 torr [0.64 +/- 0.06 kPa]; p = NS). Increases in the pressure drop across the middle and venous vessels were transient and no longer significantly different from baseline 15 mins after smoke inhalation. Similarly, analysis of the pulmonary artery/blood flow data demonstrated that the mean slope and pressure intercept were greater than baseline only at 5 mins postsmoke inhalation (p < .05). Thromboxane B2 did not significantly change from baseline values after smoke exposure and prostaglandin F1 alpha demonstrated a slight but significant decrease 30 mins postsmoke. Pulmonary edema was measured gravimetrically (wet/dry weight ratio) and smoke significantly increased lung water in the left lower lobe (wet/dry weight ratio = 6.55 +/- 0.4) as compared with the normal left upper lobe (wet/dry weight ratio = 4.97 +/- 0.2).

CONCLUSIONS

We conclude that smoke causes an intense but transient increase in the pressure drop across the venous segment that may accelerate the formation of pulmonary edema, which is not mediated by changes in thromboxane B2 or prostaglandin F1 alpha.

Effects of wood and cotton smoke on the surface properties of pulmonary surfactant

The effects of wood and cotton smoke and several known smoke components on the dynamic surface activity of pulmonary surfactant were characterized with a modified Wilhelmy balance. Surfactant was harvested by saline lavage from dog lungs, placed in the balance and a control surface tension/area isotherm (y-A) and surface tension at minimum area (control y/min = 6.6 +/- 1.6 dynes/cm) measured. Hysteresis area (HA), recruitment index (RI), and stability index (SI) were calculated. Following control measurements, smoke (wood or cotton) was gently blown over the surfactant in the balance. Similarly, each of the individual smoke components or Liquid smoke (prepared by bubbling wood smoke through saline) were injected onto the balance. Wood smoke significantly (P < 0.05) altered all surface properties measured, increasing ymin (22.0 +/- 1.6 dynes/cm) and decreasing HA, RI, and SI as compared to control; cotton smoke exposure had almost no effect on surfactant function. A supplementary dose of surfactant was added to the balance, following wood smoke exposure, which decreased ymin (9.4 +/- 2.6 dynes/cm, P = NS vs control) but not the other parameters to control. Acrolein, formaldehyde, and HCl had little effect on any of the surface properties measured whereas isobutyraldehyde and liquid smoke altered the y-A curve but did not increase ymin. These data demonstrate that wood but not cotton smoke inhibit surfactant function, however, surfactant function can be restored, following deactivation by smoke, suggesting that surfactant replacement therapy for victims of severe smoke inhalation may be of benefit.

Comparison of high-frequency jet to conventional mechanical ventilation in the treatment of severe smoke inhalation injury

The pathophysiology of smoke inhalation includes surfactant inhibition and pulmonary vascular injury leading to a high permeability pulmonary oedema. It has been shown in surfactant deficient animal models that methods of ventilation (i.e. high-frequency ventilation - HFV) avoiding a large pressure excursion (i.e. pressure change from end expiration to peak inspiration) improves oxygenation and decreases hyaline membrane formation. Therefore, we compared HFV with conventional mechanical ventilation (CMV) on lung function in an acute animal model of smoke inhalation (SI). Mongrel dogs were anaesthetized, surgically prepared for haemodynamic and blood gas monitoring, and placed on either CMV (n = 6) or HFV (n = 7). Following baseline (BL) measurements both groups were ventilated with wood smoke for 10 min. Ventilator settings were not adjusted from baseline following smoke inhalation in either groups; positive and expiratory pressure (PEEP, approximately 6 mmHg) was added in both groups following smoke exposure. At the conclusion of the study (4 h postsmoke inhalation) lung samples were taken for surfactant function and lung water measurements. Smoke inhalation immediately increased the A-a gradient (CMV-BL = 6.9 +/- 2.4 to CMV-SI = 77.3 +/- 1.9; HFV-BL = 10.5 +/- 2.7; HFV-SI = 72.8 +/- 3.7 mmHg), venous admixture (CMV-BL = 6.9 +/- 2.8 to CMV-SI 69.8 +/- 6.6; HFV-BL = 7 +/- 1.7 to HFV-SI = 60.4 +/- 7.9 per cent) and decreased Pao2 (CMV-BL = 110 +/- 3.4 to CMV-SI = 28 +/- 3.5; HFV-BL = 103 +/- 3.6 to HFV-SI = 31 +/- 1.7 mmHg) to a similar level in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Lung injury after experimental smoke inhalation: particle-associated changes in alveolar macrophages

The role of smoke particles in the pathogenesis of smoke inhalation lung injury is enigmatic. We report an experimental model that facilitates study of this issue. Mice were exposed over a 30-min period to smoke released from a flexible polyurethane foam, heated at 400 degrees C. The smoke was initially rich in spherical, isocyanate-containing particles of respirable sizes. Respirations were labored at the end of the exposure and worsened with time and were accompanied by increases in lung water. Bronchoalveolar lavage revealed a significant reduction in the total number of alveolar macrophages in the fluid recovered from the lungs as early as 2 hr after exposure. Macrophage cytoplasm contained numerous smoke particles and decreased numbers of lysosomal-like granules, and the nuclei were often pyknotic. The same recovered lavage fluid contained numerous smoke particles, free lysosomal-like granules, cytoplasmic and nuclear debris, and significant increases in the soluble activity of both the lysosomal marker enzyme and total protein. These findings indicate that there was cell breakdown, including macrophages. Free-radical isocyanates are toxic compounds, and we suggest that after being phagocytized these compounds contribute to the breakdown of macrophages. A pathogenic relationship between these macrophage changes and the acute lung injury can next be explored in this model.

Exosurf treatment following wood smoke inhalation

Pulmonary surfactant deactivation is an important factor in the pathophysiology caused by wood smoke inhalation. Surfactant replacement is beneficial in treatment of surfactant-deficient neonates and possibly the adult respiratory distress syndrome (ARDS). In this study, the effect of exogenous Exosurf treatment for acute wood smoke injury was examined in four groups of rabbits. All groups were anaesthetized, placed on a ventilator, and surgically prepared for haemodynamic, peak airway pressure (P(aw)), and blood gas measurements. Rabbits were monitored for 2 h following smoke or sham smoke inhalation. At the conclusion of the experiment pulmonary oedema and surfactant function were measured. A Control group (n = 5) was followed without intervention. A Smoke group (n = 4) was ventilated with wood smoke for 3 min. A third group (Smoke+Exo, n = 4) was subjected to smoke followed by pulmonary instillation of Exosurf (5 ml/kg). Saline (5 ml/kg) was instilled into the lungs of the fourth group (n = 3) as a control for Exosurf instillation. Saline, Smoke and Smoke+Exo all significantly lowered PO2 and elevated P(aw) compared to baseline and the Control group. Exosurf treatment did not reduce the pulmonary oedema or restore surfactant function caused by smoke exposure. This study indicates that wood smoke inhalation acutely damages the lung and that administration of Exosurf by instillation is not an effective treatment.

Smoke inhalation: diagnosis and treatment

Smoke inhalation, defined as airway or pulmonary parenchymal injury resulting from the inhalation of toxic combustion products, presents with a wide range of severity in patients with and without skin burns. In patients with severe injuries, the diagnosis is obvious on the basis of the history and clinical presentation; in patients with less severe injuries or those in whom the clinical consequences are delayed, diagnostic precision is difficult because diagnostic clues provide only indirect information. There is no specific treatment so diagnosis is not critical for patient management. Patients at risk include 20% to 30% of flame burn victims who should receive vigorous supportive care. The mortality rate of smoke inhalation victims without a burn is < 10%. With a burn the mortality rate is 30% to 50%, suggesting that thermal injury or its treatment is responsible for further lung damage. Endotracheal intubation provides definitive treatment for obstructed or soon-to-be obstructed patients. However the diagnosis of smoke inhalation per se is not an indication for airway intubation and respiratory support; 12% of patients without a burn require intubation versus 62% of those with a burn. A translaryngeal tube can be converted to a tracheotomy safely in burn victims; tracheotomies are easier to manage if burns of the neck are excised and grafted prior to placement. Mechanical ventilation with positive end expiratory pressure (PEEP) is the treatment for the pulmonary injury. The early lesions of smoke inhalation often progress in the context of sepsis and other complications of the burn illness to a clinical state consistent with adult respiratory distress syndrome.

Methylprednisolone does not protect the lung from inhalation injury

Most clinical studies suggest that corticosteroids are contraindicated in the treatment of acute smoke inhalation. However, they are still used in critical situations with the hope that they might reverse the acute pathophysiological responses to smoke inhalation and thus reduce the severity of the illness or make survival possible. These experiments were done to study the effect of methylprednisolone on the response to smoke inhalation in anaesthetized mongrel dogs. Three experimental protocols were followed: (I) haemodynamics, gas exchange, lung compliance, and lung water were evaluated; (II) pulmonary vascular permeability was assessed by cannulating the afferent tracheobronchial lymphatic and calculating the osmotic reflection coefficient (sigma d) at high lung lymph flows; (III) pulmonary surfactant function was studied using a Wilhelmy balance. Methylprednisolone alone did not alter any measured values compared with those seen in control animals. Treatment with methylprednisolone (30 mg/kg) prior to smoke exposure did not attenuate any of the adverse responses typically seen after smoke inhalation. These data indicate that methylprednisolone does not protect the lung from the acute physiological consequences of inhalation injury.

Smoke inhalation

An attempt has been made to review the characteristics of fire and smoke and the epidemiology of smoke inhalation to identify some of the many variables which interact to control the severity of the injury. An experimental model appropriate to study the pulmonary injury of smoke victims who survive to enter the health care system is described. Experiments which define how smoke damages the lung are reviewed in an effort to explain why the smoke-damaged lung is vulnerable to additional stress and why those with an injured lung and a burn have such a high mortality rate.

Clearance of aerosolized 99mTc-diethylenetriaminepentacetate before and after smoke inhalation

The pulmonary clearance of aerosolized 99mTc-diethylenetriaminepentacetate (DTPA) was studied in mongrel dogs immediately after exposure to wood smoke to see if a sensitive, objective way of assessing the degree of pulmonary injury might be found. Animals were studied in four groups as follows: control, following five minutes, two minutes, and 15 seconds of smoke exposure. Chest roentgenograms and 133Xe scans were taken before and after smoke exposure. The DTPA clearance was more sensitive in detecting injury than either of these imaging techniques. The DTPA clearance rates increased in a dose responsive way following smoke inhalation: 2.4 percent and 12.1 percent excreted per minute for control animals and those exposed to five minutes of smoke, respectively. Seven patients in a clinical trial of DTPA following smoke exposure are described; their DTPA clearance rates were all normal, although five were active cigarette smokers. Despite encouraging results in animal experiments, DTPA clearance studies may be of little practical value in the clinical setting of acute inhalation injury.